Simplified follower servomechanism

Claim 1

A follower servomechanism comprising: a housing having a chamber therein; a piston longitudinally displaceable in said housing to divide said housing into first and second variable compartments formed in part by opposite faces of said piston, said piston having an integral number extending through said second compartment and through an opening in said housing to the exterior thereof, the cross-sectional area of said plunger being such that the effective area of the piston face exposed to said first compartment is greater than the effective area of the piston exposed to said second compartment, said piston and plunger having a longitudinal bore therien having an open end at a surface exposed to said first chamber, said piston comprising a generally L-shaped extension integral with said piston and having an output shaft extending from said L-shaped extension through said first compartment to the exterior of said housing, said L-shaped extension and said output shaft having a closed end bore coaxial with said longitudinal bore; said piston having a bleed orifice for providing a bleed passage for fluid between said first and second compartments; a tubular element having a smooth cylindrical outer surface, said tubular element telescoping through said longitudinal piston bore to a close fit therewith from a first end exterior of said housing, said tubular element having a second end which is open and extends into said closed end bore to prevent buildup of pressure therein, said tubular element having a returning port in the side wall thereof registering with the open end of said piston bore to form a variable area orifice, and an opening adjacent said first end to permit discharge of fluid from the interior of said tubular element; a spring positioned in said output shaft and acting on the opposite side of said tubular element to stabilize its motion; said closed enD bore providing means for preventing flow of fluid from a second end of said tubular element so that said variable area orifice controls the flow of fluid from said first compartment through the interior of said tubular element to its first end thereby varying the pressure on opposite faces of said piston to displace it relative to said tubular element to meter the flow through said variable area orifice; whereby displacement of said tubular element from an initial position in which a force balance exists across said piston to another final position, produces a pressure differential across said piston causing an equal displacement to re-establish a force balance across said piston.